1. Field of the Invention
This invention relates to a roller of variable outer diameter type, and a transferring apparatus and method using the same. More particularly, it relates to a transferring apparatus and method for shifting articles transported by using rollers of variable outer diameter type, the transferring apparatus including a conveyer apparatus having such rollers of variable outer diameter type mounted on a shaft driven by a motor to transport an article, and other conveyer means, for example a belt conveyer, a chain conveyer or a roller conveyer (including one having rollers having a smaller outer diameter), arranged in the vicinity of a conveyer apparatus using such rollers of variable outer diameter type.
2. Description of the Related Art
A roller of variable outer diameter type used to vary the size of an outer diameter of a roller by using a fluid such as a compressed air, has been proposed, for example, in Japanese Patent Application Unexamined Publication Nos. 3-20420 and 3-259843 in which an elastic cylindrical pressure chamber (including a combination of a plurality of pressure chambers) secured to a rotary shaft(s) is supplied with compressed air to cause the cylindrical elastic body to expand to thus vary its diameter. Also, in shifting articles from one to another, an actuator such as a cylinder using air or hydraulic pressure may be interposed.
However, all of the above-mentioned devices have an elastic cylindrical body expanded by pressure of a fluid supplied thereinto so as to change the outer diameter size of the elastic cylindrical body. Typically, the pressure of compressed air supplied under centralized control in a factory is in a range of from about 4.5 Kgf/cm.sup.2 to about 8.5 Kgf/cm.sup.2 and hence widely varies in the pressure range to be unstable.
In the case of the above conventional roller, when the ratio of the outer diameter size of an elastic cylindrical body in the expansion state thereof to that in the normal state thereof is large (i.e. the coefficient of expansion being large), even if it is formed of a flexible elastic body such as a rubber, it is highly probable that the repetition of expansion, accompanying with an elastic strain of more than 50%, in excess of 200,000 times will cause its fatigue fracture due to the tension thereof. It is extremely difficult to obtain elastic material at low cost in order to meet this problem.
When high pressure fluid, for example, a high pressure compressed air of about 5.5 kgf/cm.sup.2 or more, is used to transport heavy load articles, the tension in the circumferential direction of the cylindrical elastic body at the time of expansion in the above conventional devices is extremely enlarged. Rubber or other elastic materials restricts the structure and the fatigue-resistance factor so that their use is made extremely difficult.
It is also noted in the conventional cylindrical elastic body that the outer diameter size thereof changes in accordance with the changing of the inner pressure thereof. Accordingly, in order to make the outer diameter size thereof constant at the time of the expansion, it is necessary to control the supplied fluid pressure with high accuracy. As a result, the structure becomes complicated, and further an expensive, high-performance pressure sensor and pressure control unit are required. Further, inasmuch as transported articles may have varied bottom configurations and may have metallic members with acute projections, there is an undesirable high possibility that when such portions with acute projections make direct contact with the cylindrical elastic body made of rubber member, a fracture of the latter is caused in a short period of time.
Moreover, a carrying apparatus in which an actuator is interposed is complicated in structure and high in cost, and requires a prolonged time period in a shifting operation.